Replacing vacuum advance

If it's mechanical, electrical or just downright confusing, this is the place to find and share answers.
Post Reply
User avatar
Registered Member
Posts: 390
Joined: 06 Aug 2017, 07:26
Location: Houston

Replacing vacuum advance


Post by JETEXAS » 22 Feb 2018, 15:26

I keep thinking I'll have my 67 Standard back on the road soon, but every long drive I take, I end up with 2 or 3 new failures.

It seems my vacuum advance has failed. It started with slight surging at light throttle and then got worse and worse over the next few drives until the engine speed rolls up and down at idle and I get a big lag and surge when I accelerate from a stop.

If I unplug the vacuum advance and cap the nozzle on the carb, all problems disappear -- confirming my hypothesis that it was the vacuum advance.

I see that it's about $25 for a standard replacement vacuum advance canister, but on the CJPonyParts site there's a bunch of complaints about them not fitting correctly or needing new holes drilled, etc. Then there's the $50 Scott Drake dual advance unit. On both of those units, how do I know it's the right amount of advance?

Then there's adjustable units although I'm not sure they'll fit.

Then there's the option of just going with an entirely new distributor -- Cardone, MSD, Pertronix, HEI style, etc.

Obviously, the cheapest and easiest option is to leave it disconnected and move on with my life, but I can't stand leaving something broken.

Any advice on the best vacuum advance replacement for a stock distributor?

Any advice on the best distributor upgrade? (And does upgrading the distributor do much for performance and mpg?)

User avatar
Registered Member
Posts: 1027
Joined: 22 Oct 2011, 05:40
Location: Berlin Wisconsin USA

Re: Replacing vacuum advance


Post by Yorgle » 22 Feb 2018, 16:40

Nearly all of the parts store replacement single-advance units I've bought are actually adjustable - even if they don't claim to be.
1968 XR-7 Augusta Green, J-Code, 5 litre, Autolite 6100, 5 spd, convertible with heated seats, cruise control and rear sway bar.

BTW, I think electronic ignition is pointless.

User avatar
Site Admin
Site Admin
Posts: 4424
Joined: 23 Dec 2010, 21:02
Location: Cave Creek, AZ

Re: Replacing vacuum advance


Post by xr7g428 » 22 Feb 2018, 18:16

Factory service manual has the specs to adjust it to.
Bill Basore, Editor / Publisher
Legendary Cougar Magazine
Currently in the Cat House
'67 XR7 GT 390 4 speed, AC, AM FM, Lime Frost Green
'68 XR7-G 428CJ C6, Tilt-Away, AM, Black Cherry
'68 XR7-G 390 4 speed, Sunroof, Cardinal Red
'68 XR7 GT-E 427 C6 AM Cardinal Red
'68 XR7 resto mod 351W, soon to be AOD, Black Cherry

Registered Member
Posts: 430
Joined: 14 Nov 2012, 21:33

Re: Replacing vacuum advance


Post by ClawIt » 23 Feb 2018, 07:04

Verify your initial timing is correct. You could have too much advance with the vacuum hooked up.
You could try hooking up the vacuum advance and loosen the dist. start the engine and retard the timing and see if the idle problems go away. If they do tighten the dist. and then give it a road trip.

User avatar
Registered Member
Posts: 120
Joined: 20 Dec 2016, 12:15
Location: Perkasie, PA

Re: Replacing vacuum advance


Post by mfc133 » 23 Feb 2018, 10:22

I just put a Standard Motor Products VC31 on my distributor and it fit no problem. I haven't run the engine yet to say how well it works but fitment was perfect.

1968 Cougar Standard, 302 4V, auto, Madras Blue

Post Reply